Enhanced spatial ALD of metals through controlled precursor mixing

ABSTRACT

Methods of depositing a film by atomic layer deposition are described. The methods comprise exposing a substrate surface to a first process condition comprising a first reactive gas and a second reactive gas and exposing the substrate surface to a second process condition comprising the second reactive gas. The first process condition comprises less than a full amount of the second reactive gas for a CVD process.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/959,972, filed Apr. 23, 2018, which is a continuation-in-part of U.S.patent application Ser. No. 15/461,842, filed Mar. 17, 2017, which isnow U.S. Pat. No. 10,985,023, issued Apr. 20, 2021, which iscontinuation of U.S. patent application Ser. No. 14/965,349, filed Dec.10, 2015, which is now U.S. Pat. No. 9,601,339, issued Mar. 21, 2017,which is a continuation of U.S. patent application Ser. No. 14/062,804,filed Oct. 24, 2013, which is now U.S. Pat. No. 9,230,815, issued Jan.5, 2016, which claims priority to U.S. Provisional Application Nos.61/719,350, filed Oct. 26, 2012, 61/784,281, filed Mar. 14, 2013 and61/825,983, filed May 21, 2013; U.S. patent application Ser. No.15/959,972, filed Apr. 23, 2018 is a continuation-in-part of U.S. patentapplication Ser. No. 15/494,892, filed Apr. 24, 2017, now abandoned,which claims priority to U.S. Provisional Application No. 62/327,091,filed Apr. 25, 2016, the entire disclosures of which are herebyincorporated by reference herein.

TECHNICAL FIELD

The present disclosure relates generally to apparatus and methods ofdepositing thin films. In particular, the disclosure relates toapparatus and methods for depositing spatial ALD films with controlledprecursor mixing.

BACKGROUND

Spatial ALD relies on spatial separation of precursors. Film growthhappens when a substrate moves from one precursor zone to another. Asthe substrate repeatedly moves between the two zones, continual growthis realized. One example is tungsten spatial ALD in which one precursorzone is filled with WF₆ and another precursor zone is filled with H₂. Ineach zone, the precursor may or may not be diluted with argon. Oneexposure cycle means the substrate having travelled through one WF₆ zoneand one H₂ zone.

Growth rates are typically below 0.2 angstroms/cycle for the spatial ALDof tungsten at substrate temperatures between 200 and 450 degreesCelsius. There is a need in the art for methods of depositing films byspatial ALD with greater growth rates.

SUMMARY

One or more embodiments of the disclosure are directed to methods ofdepositing a film by atomic layer deposition. The methods compriseexposing a substrate surface to a first process condition comprising afirst reactive gas and a second reactive gas and exposing the substratesurface to a second process condition comprising the second reactivegas. The first process condition comprises less than a full amount ofthe second reactive gas for a CVD process.

Additional embodiments of the disclosure are directed to methodscomprising exposing a substrate surface to a first process conditioncomprising a first reactive gas and a second reactive gas. The firstreactive gas and the second reactive gas being spontaneously reactive.The substrate surface is exposed to a second process conditionconsisting essentially of the second reactive gas. The first processcondition comprises less than a full amount of the second reactive gasfor CVD.

Further embodiments of the disclosure are directed to methods comprisingexposing a substrate surface to a first process condition in a firstprocess region of a processing chamber. The first process conditioncomprises a constant flow of a first reactive gas comprising WF₆ and apulsed flow of a second reactive gas consisting essentially of H₂. Thesecond reactive gas pulsed so that there is less than a full amount ofthe second reactive gas for CVD. The substrate is laterally movedthrough a gas curtain from the first process region to a second processregion of the processing chamber. The gas curtain comprising one or moreof a purge gas stream and/or a vacuum region. The substrate surface isexposed to a second process condition in the second process region. Thesecond process condition consisting essentially of H₂. The substrate islaterally moved through a gas curtain from the second process region.The gas curtain comprises one or more of a purge gas stream and/or avacuum region. Exposures to the first process condition and the secondprocess condition are repeated to deposit a film of a predeterminedthickness.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this disclosure and are therefore not to beconsidered limiting of its scope, for the disclosure may admit to otherequally effective embodiments.

FIG. 1 shows a cross-sectional view of a batch processing chamber inaccordance with one or more embodiment of the disclosure;

FIG. 2 shows a partial perspective view of a batch processing chamber inaccordance with one or more embodiment of the disclosure;

FIG. 3 shows a schematic view of a batch processing chamber inaccordance with one or more embodiment of the disclosure;

FIG. 4 shows a schematic view of a portion of a wedge shaped gasdistribution assembly for use in a batch processing chamber inaccordance with one or more embodiment of the disclosure;

FIG. 5 shows a schematic view of a batch processing chamber inaccordance with one or more embodiment of the disclosure; and

FIG. 6 illustrates an exemplary process sequence for the formation of atungsten layer using a two pulse cyclical deposition technique accordingto one embodiment described herein;

DETAILED DESCRIPTION

Before describing several exemplary embodiments of the disclosure, it isto be understood that the disclosure is not limited to the details ofconstruction or process steps set forth in the following description.The disclosure is capable of other embodiments and of being practiced orbeing carried out in various ways.

A “substrate” as used herein, refers to any substrate or materialsurface formed on a substrate upon which film processing is performedduring a fabrication process. For example, a substrate surface on whichprocessing can be performed include materials such as silicon, siliconoxide, strained silicon, silicon on insulator (SOI), carbon dopedsilicon oxides, amorphous silicon, doped silicon, germanium, galliumarsenide, glass, sapphire, and any other materials such as metals, metalnitrides, metal alloys, and other conductive materials, depending on theapplication. Substrates include, without limitation, semiconductorwafers. Substrates may be exposed to a pretreatment process to polish,etch, reduce, oxidize, hydroxylate, anneal and/or bake the substratesurface. In addition to film processing directly on the surface of thesubstrate itself, in the present disclosure, any of the film processingsteps disclosed may also be performed on an under-layer formed on thesubstrate as disclosed in more detail below, and the term “substratesurface” is intended to include such under-layer as the contextindicates. Thus for example, where a film/layer or partial film/layerhas been deposited onto a substrate surface, the exposed surface of thenewly deposited film/layer becomes the substrate surface.

As used in this specification and the appended claims, the terms“precursor”, “reactant”, “reactive gas” and the like are usedinterchangeably to refer to any gaseous species that can react with thesubstrate surface.

Some embodiments of the disclosure are directed to processes that use areaction chamber with multiple gas ports that can be used forintroduction of different chemicals or plasma gases. Spatially, thesegas ports (also referred to as channels) are separated by inert purginggases and/or vacuum pumping holes to create a gas curtain that minimizesor eliminates mixing of gases from different gas ports to avoid unwantedgas phase reactions. Wafers moving through these different spatiallyseparated ports get sequential and multiple surface exposures todifferent chemical or plasma environment so that layer by layer filmgrowth in spatial ALD mode or surface etching process occur. In someembodiments, the processing chamber has modular architectures on gasdistribution components and each modular component has independentparameter control (e.g., RF or gas flow) to provide flexibility tocontrol, for example, gas flow and/or RF exposure.

Embodiments of the disclosure are directed to apparatus and methods toprovide enhanced chemical exchange in a batch processing chamber, alsoreferred to as a spatial processing chamber. FIG. 1 shows across-section of a processing chamber 100 including a gas distributionassembly 120, also referred to as injectors or an injector assembly, anda susceptor assembly 140. The gas distribution assembly 120 is any typeof gas delivery device used in a processing chamber. The gasdistribution assembly 120 includes a front surface 121 which faces thesusceptor assembly 140. The front surface 121 can have any number orvariety of openings to deliver a flow of gases toward the susceptorassembly 140. The gas distribution assembly 120 also includes an outeredge 124 which in the embodiments shown, is substantially round.

The specific type of gas distribution assembly 120 used can varydepending on the particular process being used. Embodiments of thedisclosure can be used with any type of processing system where the gapbetween the susceptor and the gas distribution assembly is controlled.In a binary reaction, the plurality of gas channels can include at leastone first reactive gas A channel, at least one second reactive gas Bchannel, at least one purge gas P channel and/or at least one vacuum Vchannel. The gases flowing from the first reactive gas A channel(s), thesecond reactive gas B channel(s) and the purge gas P channel(s) aredirected toward the top surface of the wafer. Some of the gas flow moveshorizontally across the surface of the wafer and out of the processregion through the purge gas P channel(s). A substrate moving from oneend of the gas distribution assembly to the other end will be exposed toeach of the process gases in turn, forming a layer on the substratesurface.

In some embodiments, the gas distribution assembly 120 is a rigidstationary body made of a single injector unit. In one or moreembodiments, the gas distribution assembly 120 is made up of a pluralityof individual sectors (e.g., injector units 122), as shown in FIG. 2 .Either a single piece body or a multi-sector body can be used with thevarious embodiments of the disclosure described.

A susceptor assembly 140 is positioned beneath the gas distributionassembly 120. The susceptor assembly 140 includes a top surface 141 andat least one recess 142 in the top surface 141. The susceptor assembly140 also has a bottom surface 143 and an edge 144. The recess 142 can beany suitable shape and size depending on the shape and size of thesubstrates 60 being processed. In the embodiment shown in FIG. 1 , therecess 142 has a flat bottom to support the bottom of the wafer;however, the bottom of the recess can vary. In some embodiments, therecess has step regions around the outer peripheral edge of the recesswhich are sized to support the outer peripheral edge of the wafer. Theamount of the outer peripheral edge of the wafer that is supported bythe steps can vary depending on, for example, the thickness of the waferand the presence of features already present on the back side of thewafer.

In some embodiments, as shown in FIG. 1 , the recess 142 in the topsurface 141 of the susceptor assembly 140 is sized so that a substrate60 supported in the recess 142 has a top surface 61 substantiallycoplanar with the top surface 141 of the susceptor 140. As used in thisspecification and the appended claims, the term “substantially coplanar”means that the top surface of the wafer and the top surface of thesusceptor assembly are coplanar within ±0.5 mm. In some embodiments, thetop surfaces are coplanar within ±0.4 mm, 0.3 mm, ±0.2 mm, 0.15 mm, 0.10mm or ±0.05 mm.

The susceptor assembly 140 of FIG. 1 includes a support post 160 whichis capable of lifting, lowering and rotating the susceptor assembly 140.The susceptor assembly may include a heater, or gas lines, or electricalcomponents within the center of the support post 160. The support post160 may be the primary means of increasing or decreasing the gap betweenthe susceptor assembly 140 and the gas distribution assembly 120, movingthe susceptor assembly 140 into proper position. The susceptor assembly140 may also include fine tuning actuators 162 which can makemicro-adjustments to susceptor assembly 140 to create a predeterminedgap 170 between the susceptor assembly 140 and the gas distributionassembly 120.

In some embodiments, the gap 170 distance is in the range of about 0.1mm to about 5.0 mm, or in the range of about 0.1 mm to about 3.0 mm, orin the range of about 0.1 mm to about 2.0 mm, or in the range of about0.2 mm to about 1.8 mm, or in the range of about 0.3 mm to about 1.7 mm,or in the range of about 0.4 mm to about 1.6 mm, or in the range ofabout 0.5 mm to about 1.5 mm, or in the range of about 0.6 mm to about1.4 mm, or in the range of about 0.7 mm to about 1.3 mm, or in the rangeof about 0.8 mm to about 1.2 mm, or in the range of about 0.9 mm toabout 1.1 mm, or about 1 mm.

The processing chamber 100 shown in the Figures is a carousel-typechamber in which the susceptor assembly 140 can hold a plurality ofsubstrates 60. As shown in FIG. 2 , the gas distribution assembly 120may include a plurality of separate injector units 122, each injectorunit 122 being capable of depositing a film on the wafer, as the waferis moved beneath the injector unit. Two pie-shaped injector units 122are shown positioned on approximately opposite sides of and above thesusceptor assembly 140. This number of injector units 122 is shown forillustrative purposes only. It will be understood that more or lessinjector units 122 can be included. In some embodiments, there are asufficient number of pie-shaped injector units 122 to form a shapeconforming to the shape of the susceptor assembly 140. In someembodiments, each of the individual pie-shaped injector units 122 may beindependently moved, removed and/or replaced without affecting any ofthe other injector units 122. For example, one segment may be raised topermit a robot to access the region between the susceptor assembly 140and gas distribution assembly 120 to load/unload substrates 60.

Processing chambers having multiple gas injectors can be used to processmultiple wafers simultaneously so that the wafers experience the sameprocess flow. For example, as shown in FIG. 3 , the processing chamber100 has four gas injector assemblies and four substrates 60. At theoutset of processing, the substrates 60 can be positioned between thegas distribution assemblies 120. Rotating 17 the susceptor assembly 140by 45° will result in each substrate 60 which is between gasdistribution assemblies 120 to be moved to an gas distribution assembly120 for film deposition, as illustrated by the dotted circle under thegas distribution assemblies 120. An additional 45° rotation would movethe substrates 60 away from the gas distribution assemblies 120. Thenumber of substrates 60 and gas distribution assemblies 120 can be thesame or different. In some embodiments, there are the same numbers ofwafers being processed as there are gas distribution assemblies. In oneor more embodiments, the number of wafers being processed are fractionof or an integer multiple of the number of gas distribution assemblies.For example, if there are four gas distribution assemblies, there are 4xwafers being processed, where x is an integer value greater than orequal to one. In an exemplary embodiment, the gas distribution assembly120 includes eight process regions separated by gas curtains and thesusceptor assembly 140 can hold six wafers.

The processing chamber 100 shown in FIG. 3 is merely representative ofone possible configuration and should not be taken as limiting the scopeof the disclosure. Here, the processing chamber 100 includes a pluralityof gas distribution assemblies 120. In the embodiment shown, there arefour gas distribution assemblies (also called gas distributionassemblies 120) evenly spaced about the processing chamber 100. Theprocessing chamber 100 shown is octagonal; however, those skilled in theart will understand that this is one possible shape and should not betaken as limiting the scope of the disclosure. The gas distributionassemblies 120 shown are trapezoidal, but can be a single circularcomponent or made up of a plurality of pie-shaped segments, like thatshown in FIG. 2 .

The embodiment shown in FIG. 3 includes a load lock chamber 180, or anauxiliary chamber like a buffer station. This chamber 180 is connectedto a side of the processing chamber 100 to allow, for example thesubstrates (also referred to as substrates 60) to be loaded/unloadedfrom the chamber 100. A wafer robot may be positioned in the chamber 180to move the substrate onto the susceptor.

Rotation of the carousel (e.g., the susceptor assembly 140) can becontinuous or intermittent (discontinuous). In continuous processing,the wafers are constantly rotating so that they are exposed to each ofthe injectors in turn. In discontinuous processing, the wafers can bemoved to the injector region and stopped, and then to the region 84between the injectors and stopped. For example, the carousel can rotateso that the wafers move from an inter-injector region across theinjector (or stop adjacent the injector) and on to the nextinter-injector region where the carousel can pause again. Pausingbetween the injectors may provide time for additional processing stepsbetween each layer deposition (e.g., exposure to plasma).

FIG. 4 shows a sector or portion of a gas distribution assembly 220,which may be referred to as an injector unit 122. The injector units 122can be used individually or in combination with other injector units.For example, as shown in FIG. 5 , four of the injector units 122 of FIG.4 are combined to form a single gas distribution assembly 220. (Thelines separating the four injector units are not shown for clarity.)While the injector unit 122 of FIG. 4 has both a first reactive gas port125 and a second gas port 135 in addition to purge gas ports 155 andvacuum ports 145, an injector unit 122 does not need all of thesecomponents.

Referring to both FIGS. 4 and 5 , a gas distribution assembly 220 inaccordance with one or more embodiment may comprise a plurality ofsectors (or injector units 122) with each sector being identical ordifferent. The gas distribution assembly 220 is positioned within theprocessing chamber and comprises a plurality of elongate gas ports 125,135, 145 in a front surface 121 of the gas distribution assembly 220.The plurality of elongate gas ports 125, 135, 145, 155 extend from anarea adjacent the inner peripheral edge 123 toward an area adjacent theouter peripheral edge 124 of the gas distribution assembly 220. Theplurality of gas ports shown include a first reactive gas port 125, asecond gas port 135, a vacuum port 145 which surrounds each of the firstreactive gas ports and the second reactive gas ports and a purge gasport 155.

With reference to the embodiments shown in FIG. 4 or 5 , when statingthat the ports extend from at least about an inner peripheral region toat least about an outer peripheral region, however, the ports can extendmore than just radially from inner to outer regions. The ports canextend tangentially as vacuum port 145 surrounds reactive gas port 125and reactive gas port 135. In the embodiment shown in FIGS. 4 and 5 ,the wedge shaped reactive gas ports 125, 135 are surrounded on alledges, including adjacent the inner peripheral region and outerperipheral region, by a vacuum port 145.

Referring to FIG. 4 , as a substrate moves along path 127, each portionof the substrate surface is exposed to the various reactive gases. Tofollow the path 127, the substrate will be exposed to, or “see”, a purgegas port 155, a vacuum port 145, a first reactive gas port 125, a vacuumport 145, a purge gas port 155, a vacuum port 145, a second gas port 135and a vacuum port 145. Thus, at the end of the path 127 shown in FIG. 4, the substrate has been exposed to the first reactive gas 125 and thesecond reactive gas 135 to form a layer. The injector unit 122 shownmakes a quarter circle but could be larger or smaller. The gasdistribution assembly 220 shown in FIG. 5 can be considered acombination of four of the injector units 122 of FIG. 4 connected inseries. The path 127 shown in FIG. 4 is represented ascounter-clockwise; however, those skilled in the art will understandthat the path can be reversed and/or the order of gas ports can bereversed.

The injector unit 122 of FIG. 4 shows a gas curtain 150 that separatesthe reactive gases. The term “gas curtain” is used to describe anycombination of gas flows or vacuum that separate reactive gases frommixing. The gas curtain 150 shown in FIG. 4 comprises the portion of thevacuum port 145 next to the first reactive gas port 125, the purge gasport 155 in the middle and a portion of the vacuum port 145 next to thesecond gas port 135. This combination of gas flow and vacuum can be usedto prevent or minimize gas phase reactions of the first reactive gas andthe second reactive gas.

Referring to FIG. 5 , the combination of gas flows and vacuum from thegas distribution assembly 220 form a separation into a plurality ofprocess regions 250. The process regions are roughly defined around theindividual gas ports 125, 135 with the gas curtain 150 between 250. Theembodiment shown in FIG. 5 makes up eight separate process regions 250with eight separate gas curtains 150 between. A processing chamber canhave at least two process region. In some embodiments, there are atleast three, four, five, six, seven, eight, nine, 10, 11 or 12 processregions.

During processing a substrate may be exposed to more than one processregion 250 at any given time. However, the portions that are exposed tothe different process regions will have a gas curtain separating thetwo. For example, if the leading edge of a substrate enters a processregion including the second gas port 135, a middle portion of thesubstrate will be under a gas curtain 150 and the trailing edge of thesubstrate will be in a process region including the first reactive gasport 125.

A factory interface 280, which can be, for example, a load lock chamber,is shown connected to the processing chamber 100. A substrate 60 isshown superimposed over the gas distribution assembly 220 to provide aframe of reference. The substrate 60 may often sit on a susceptorassembly to be held near the front surface 121 of the gas distributionassembly 120. The substrate 60 is loaded via the factory interface 280into the processing chamber 100 onto a substrate support or susceptorassembly (see FIG. 3 ). The substrate 60 can be shown positioned withina process region because the substrate is located adjacent the firstreactive gas port 125 and between two gas curtains 150 a, 150 b.Rotating the substrate 60 along path 127 will move the substratecounter-clockwise around the processing chamber 100. Thus, the substrate60 will be exposed to the first process region 250 a through the eighthprocess region 250 h, including all process regions between.

Embodiments of the disclosure are directed to processing methodscomprising a processing chamber 100 with a plurality of process regions250 a-250 h with each process region separated from an adjacent regionby a gas curtain 150. For example, the processing chamber shown in FIG.5 . The number of gas curtains and process regions within the processingchamber can be any suitable number depending on the arrangement of gasflows. The embodiment shown in FIG. 5 has eight gas curtains 150 andeight process regions 250 a-250 h. The number of gas curtains isgenerally equal to or greater than the number of process regions.

A plurality of substrates 60 are positioned on a substrate support, forexample, the susceptor assembly 140 shown FIGS. 1 and 2 . The pluralityof substrates 60 are rotated around the process regions for processing.Generally, the gas curtains 150 are engaged (gas flowing and vacuum on)throughout processing including periods when no reactive gas is flowinginto the chamber.

A first reactive gas A is flowed into one or more of the process regions250 while an inert gas is flowed into any process region 250 which doesnot have a first reactive gas A flowing into it. For example if thefirst reactive gas is flowing into process regions 250 b through processregion 250 h, an inert gas would be flowing into process region 250 a.The inert gas can be flowed through the first reactive gas port 125 orthe second gas port 135.

The inert gas flow within the process regions can be constant or varied.In some embodiments, the reactive gas is co-flowed with an inert gas.The inert gas will act as a carrier and diluent. Since the amount ofreactive gas, relative to the carrier gas, is small, co-flowing may makebalancing the gas pressures between the process regions easier bydecreasing the differences in pressure between adjacent regions.

Accordingly, one or more embodiments of the disclosure are directed toprocessing methods utilizing a batch processing chamber like that shownin FIG. 5 . A substrate 60 is placed into the processing chamber whichhas a plurality of sections 250, each section separated from adjacentsection by a gas curtain 150.

In some embodiments, a substrate surface is exposed to a first processcondition followed by exposure to a second process condition. As used inthis manner, the term “process condition” refers to the chemicalenvironment, temperature and pressure. The first process conditioncomprises a first reactive gas and a second reactive gas. The firstreactive gas and the second reactive gas are spontaneously reactiveunder the process conditions (e.g., temperature and pressure). Thesecond reactive gas is provided in an amount that is less than a fullamount that would be used for a chemical vapor deposition (CVD) process.

In a time-domain process, the after exposure to the first processcondition, the processing chamber is purged to replace the first processcondition with an inert environment. This also removes by-products fromthe reaction of the first reactive gas and the second reactive gas. In aspatial ALD process, like one that uses a chamber shown in FIG. 5 ,after exposure to the first process condition, the substrate can belaterally moved through a gas curtain to a second process region of theprocessing chamber. The gas curtain locally purges the first processcondition from the substrate surface to replace the first processcondition existing in the first process region. The gas curtaincomprises one or more of a purge gas stream and/or a vacuum region. Insome embodiments, as shown in FIG. 5 , the gas curtain comprises a purgegas stream bounded on either side by a vacuum region so that thesubstrate surface is exposed to, in order, a vacuum region, a purge gasstream and a second vacuum region between each of the process regions ofthe processing chamber.

After exposure to the first process condition and purging the substratesurface is exposed to a second process condition. The second processcondition can be formed in the process chamber (time-domain ALD) or in asecond process region of the processing chamber (spatial ALD). Thesecond process condition comprises the second reactive gas. In someembodiments, the second process condition consists essentially of thesecond reactive gas. As used in this regard, the term “consistsessentially of” means that the reactive species of the second reactivegas makes up greater than or equal to about 95%, 98% or 99% of thestated species on a molar basis. The percentage does not include inertgases, diluent gases or carrier gases.

After exposure to the second reactive gas, the substrate surface orprocessing chamber is purged of the second process condition. This canbe performed by purging the entire process chamber (i.e., in atime-domain process) or moving the substrate through a gas curtain to adifferent region of the processing chamber (i.e., in a spatial process).

Some embodiments of the disclosure enhance the growth rates by bleedingH₂ into the WF₆ zone in a controlled manner (first process condition).In this enhanced spatial ALD, the H₂ zone remains the same, having onlyH₂ and in some cases argon as well (second process condition). The WF₆zone now has both WF₆ and H₂. In some embodiments, argon is present aswell.

Growth rates (also called deposition rates) of greater than 0.2 Å/cyclemay be realized. In an effort to enhance growth rate to beyond 0.2Å/cycle while maintaining step coverage, a controlled amount of H₂ or anH₂/inert mixture is introduced into the WF₆ zone(s) as well. This isreferred to as enhanced spatial ALD. In some embodiments, the depositionrate is in the range of about 0.2 Å/cycle to about 1 Å/cycle.

In some embodiments, the first process condition comprises WF₆. Thefirst process condition of some embodiments comprises WF₆, H₂, and anoptional inert gas such as argon. In some embodiments, the secondprocess condition comprises H₂ and an optional inert gas such as argon.

In an exemplary embodiment, the first process condition comprises WF₆with a total flow rate in the range of about 10 to about 1000 sccm, orin the range of about 50 to about 500 sccm, or about 100 sccm. The H₂flow of the first process condition is in the range of about 1 to about100 sccm, or about 10 sccm. The argon flow of the first processcondition is in the range of about 0 to about 10000 sccm, or in therange of about 100 to about 5000 sccm, or in the range of about 500 toabout 1000 sccm, or about 890 sccm.

In some embodiments, the second process condition comprises or consistsessentially of a mixture of H₂/Ar. The percentage of H₂ in the mixturecan be in the range of about 1 to about 99%, or in the range of about 1to about 80%, or in the range of about 1 to about 60%, or in the rangeof about 2 to about 40%, or in the range of about 3 to about 20%, or inthe range of about 3 to about 10%, or about 4%.

The total H₂/Ar mixture flow can be in the range of about 1 to about10000 sccm, or in the range of about 10 to about 1000 sccm, or in therange of about 100 to about 500 sccm, or in about 250 sccm. The total H₂flow can be in the range of about 1 to about 10000 sccm, or in the rangeof about 100 to about 5000 sccm, or in the range of about 1000 to about4000 sccm, or about 2000 sccm. The total amount of argon flow can be inthe range of about 0 to about 10000 sccm. If no argon co-flow is used,the flow is 0 sccm.

The substrate temperature can be adjusted and maintained based on theprecursors being used. In some embodiments, the temperature of thesubstrate is in the range of about 200° C. to about 700° C., or in therange of about 300° C. to about 500° C., or in the range of about 325°C. to about 400° C., or about 350° C.

Suitable tungsten precursors for use with the first process conditioninclude, but are not limited, to WF₆, WCl₆, WCl₅, WOCl₄, W₂Cl₁₀, WCl₄,bis(cyclopentadienyl)tungsten(IV) chloride hydride and/or combinationsthereof. Suitable molybdenum precursors for use with the first processcondition include, but are not limited to, MoF₆, MoCl₅, MoOCl₄, MoCl₃and/or combinations thereof.

Exposure to the first process condition and the second process conditioncan be repeated to deposit a film having a predetermined thickness. In atime-domain process, the processing chamber is purged between eachprocess condition exposure. In a spatial process, the substrate is movedamong different process regions of the processing chamber wheredifferent process regions have different process conditions. Forexample, referring to FIG. 5 , process regions 250 a, 250 c, 250 e and250 g may have the first process condition and process regions 250 b,250 d, 250 f and 250 h may have the second process condition. Asubstrate rotated through a complete circle would be exposed to fourrepeated sequences of the first process condition and the second processcondition.

In some embodiments, the film deposited is a tungsten-containing layer.In some embodiments, the film deposited is a molybdenum containinglayer. An exemplary process is described herein as it relates to forminga tungsten-containing layer. One skilled in the art will recognize thatthe exemplary method described herein may be adapted to the depositionof other films.

FIG. 6 depicts a method for forming a tungsten-containing layer on asubstrate in accordance with some embodiments of the invention. Themethod 600 generally begins at 602, where a substrate, having a surfaceupon which a tungsten-containing layer is to be formed is provided andplaced into a processing chamber. As used herein, a “substrate surface”refers to any substrate surface upon which a layer may be formed. Thesubstrate surface may have one or more features formed therein, one ormore layers formed thereon, and combinations thereof. The substrate (orsubstrate surface) may be pretreated prior to the deposition of thetungsten-containing layer, for example, by polishing, etching,reduction, oxidation, halogenation, hydroxylation, annealing, baking, orthe like.

The substrate may be any substrate capable of having material depositedthereon, such as a silicon substrate, a III-V compound substrate, asilicon germanium (SiGe) substrate, an epi-substrate, asilicon-on-insulator (SOI) substrate, a display substrate such as aliquid crystal display (LCD), a plasma display, an electro luminescence(EL) lamp display, a solar array, solar panel, a light emitting diode(LED) substrate, a semiconductor wafer, or the like. In someembodiments, one or more additional layers may be disposed on thesubstrate such that the tungsten-containing layer may be at leastpartially formed thereon. For example, in some embodiments, a layercomprising a metal, a nitride, an oxide, or the like, or combinationsthereof may be disposed on the substrate and may have the tungstencontaining layer formed upon such layer or layers.

In some embodiments, the substrate may be exposed to an optional soakprocess 603 prior to beginning the cyclical deposition process to form atungsten-containing layer on the substrate (as discussed below at 604),as shown in phantom at 603. In one or more embodiments, the method 604of depositing the tungsten-containing layer on the substrate does notrequire a soaking process. This means there is substantially noadvantage to soaking prior to depositing the film. As used in thisspecification and the appended claims, the term “substantially noadvantage” used in this respect means that there is less than about a10% increase in the deposition rate or less than about a 20% differencein the conformality and uniformity of the deposited film. That beingsaid, there are embodiments which are discussed further below in which apresoak forms an important part of the overall process. In someembodiments, the soak process may comprise heating the substrate to asoak temperature followed by exposing the substrate to a soak gas. Forexample, in some embodiments, the substrate may be heated to atemperature of about 100 to about 600° C., or in some embodiments, about200° C. to about 600° C., or in some embodiments about 300° C. to about500° C., or in some embodiments about 350° C. to about 420° C., or insome embodiments about 375° C. to about 500° C.

In some embodiments, the soak gas may comprise a reducing gas comprisinga hydrogen gas and/or a hydride compound, such as silane compounds(e.g., silane, disilane, trisilane, tetrasilane, chlorosilane,dichlorosilane, tetrachlorosilane, hexachlorodisilane, methylsilane, orthe like), borane compounds (e.g., borane, diborane, triborane,tetraborane, pentaborane, alkylboranes, or the like), phosphine,ammonia, amine compounds, hydrogen, derivatives thereof, combinationsthereof, or the like. When present, the reducing gas adsorbs to and/orreacts with the substrate surface, to form a treated surface. In someembodiments, the treated surface provides a quicker deposition processfor an overall smooth and more uniform subsequently deposited layers.

In some embodiments, the substrate is subjected to a silane soak. Someof these embodiments use a silane soak that is substantially onlysilane. As used in this specification and the appended claims, the term“substantially only silane” used in this respect means that the soakingfluid is 99% silane or greater as the soaking agent. For example, a soaksolution that is 5% silane in hydrogen, would be considered 100% silaneas the diluent (hydrogen) is not included.

In some embodiments, the reducing gas contains a hydrogen/hydride flowrate ratio of about 40:1 or greater, or in some embodiments, about 100:1or greater, or in some embodiments, about 500:1 or greater, or in someembodiments, about 800:1 or greater, or in some embodiments, about1,000:1 or greater. In some embodiments, the hydride compound (e.g.,diborane) may have a flow rate of about 1 sccm to about 75 sccm, or insome embodiments, about 3 sccm to about 30 sccm, or in some embodiments,about 5 sccm to about 15 sccm. In some embodiments, the hydride compoundmay be within a carrier gas (e.g., hydrogen, nitrogen, argon, helium orthe like), such that the mixture may have a flow rate within a range ofabout 50 sccm to about 500 sccm, or in some embodiments, about 75 sccmto about 400 sccm, or in some embodiments, about 100 sccm to about 300sccm. In some embodiments, the hydrogen gas may be provided at a flowrate of about 1 slm to about 20 slm, or in some embodiments, from about3 slm to about 15 slm, or in some embodiments, from about 5 slm to about10 slm. The hydrogen/hydride flow rate ratio may be calculated bydividing the total hydrogen flow rate by the total hydride flow rate.The total hydrogen flow rate contains the sum of all sources of hydrogenincluding the flow rate of any hydrogen carrier gas and the flow rate ofany independent hydrogen gas.

In some embodiments, the reducing gas may be mixed within theprocessing/deposition chamber or outside and may be coming from multiplesources. For example, in some embodiments, the substrate is exposed tothe reducing gas which is formed by combining in the chamber a gas flowof a reducing or hydride compound and hydrogen mixture (e.g., 5% B₂H₆ inH₂) along with a gas flow of hydrogen gas. In another example, in someembodiments, the gas flow of the reducing or hydride compound andhydrogen mixture (e.g., 5% B₂H₆ in H₂) and the gas flow of hydrogen gasare combined prior to entering the chamber. Additional processparameters may be utilized to facilitate the soak process. For example,in some embodiments, the soak process may be performed while maintaininga pressure in the process chamber of about 1 Torr to about 150 Torr, orin some embodiments, from about 1 Torr to about 100 Torr, or in someembodiments, from about 10 Torr to about 50 Torr, or in someembodiments, from about 20 Torr to about 40 Torr, or in someembodiments, about 5 Torr to about 20 Torr. In some embodiments, thesoak process may be performed for a time period within of about 1 secondto about 90 seconds, or in some embodiments, less than about 60 seconds,or in some embodiments, less than about 30 seconds, or in someembodiments, less than about 10 seconds.

A “pulse” or “dose” as used herein is intended to refer to a quantity ofa source gas that is intermittently or non-continuously introduced intothe process chamber. The quantity of a particular compound within eachpulse may vary over time, depending on the duration of the pulse. Aparticular process gas may include a single compound or amixture/combination of two or more compounds, for example, the processgases described below.

The durations for each pulse/dose are variable and may be adjusted toaccommodate, for example, the volume capacity of the processing chamberas well as the capabilities of a vacuum system coupled thereto.Additionally, the dose time of a process gas may vary according to theflow rate of the process gas, the temperature of the process gas, thetype of control valve, the type of process chamber employed, as well asthe ability of the components of the process gas to adsorb onto thesubstrate surface. Dose times may also vary based upon the type of layerbeing formed and the geometry of the device being formed. A dose timeshould be long enough to provide a volume of compound sufficient toadsorb/chemisorb onto substantially the entire surface of the substrateand form a layer of a process gas component thereon.

The process of forming the tungsten-containing layer at step 604 maybegin by exposing the substrate to a first reactive gas. In someembodiments, the first reactive gas comprises a tungsten precursor (alsoreferred to as a tungsten-containing gas, and the like) and is exposedto the substrate for a first period of time, as shown at 606. Thetungsten precursor can be any suitable tungsten-containing gasincluding, but not limited to, halide based tungsten precursors or ametal-organic based tungsten precursor. For example, in someembodiments, the tungsten precursor may comprise tungsten pentachloride(WCl₅), compounds with the empirical formula of WCl₅ (e.g., W₂Cl₁₀,W₃Cl₁₅), tungsten hexachloride (WCl₆), compounds with the empiricalformula of WCl₆ (e.g., W₂Cl₁₂), tungsten hexafluoride (WF₆). In one ormore embodiments, the tungsten-containing precursor is selected from thegroup consisting of tungsten pentachloride, compounds with the empiricalformula WCl₅ and tungsten hexachloride. In some embodiments, thetungsten-containing compound comprises a compound with the empiricalformula W_(x)Cl_(5x), where x is greater than or equal to about 1 and yis greater than or equal to about 5. Without being bound by anyparticular theory of operation, it is believed that changing the anionfrom fluoride to chloride results in a larger ion which limitsdiffusion, resulting in a larger conduction. In some embodiments, thetungsten-containing film is substantially carbon free. As used in thisspecification and the appended claims, the term “substantially carbonfree” means that there is less than about 1% or 0.5% or 0.1% carbon onan atomic basis in the film.

The tungsten-containing process gas may be provided in one or morepulses or continuously. The flow rate of the tungsten-containing gas canbe any suitable flow rate including, but not limited to, flow rates isin the range of about 1 to about 5000 sccm, or in the range of about 2to about 4000 sccm, or in the range of about 3 to about 3000 sccm or inthe range of about 5 to about 2000 sccm. The tungsten-containingprecursor can be provided at any suitable pressure including, but notlimited to, a pressure in the range of about 5 mTorr to about 25 Torr,or in the range of about 100 mTorr to about 20 Torr, or in the range ofabout 5 Torr to about 20 Torr, or in the range of about 50 mTorr toabout 2000 mTorr, or in the range of about 100 mTorr to about 1000mTorr, or in the range of about 200 mTorr to about 500 mTorr.

In some embodiments, a tungsten nucleation layer is formed as part ofthe tungsten-containing layer. The tungsten nucleation layer can beformed using the same or different tungsten precursor as used in thetungsten-containing process gas. The period of time that the substrateis exposed to the tungsten-containing gas may be any suitable amount oftime necessary to allow the tungsten precursor to form an adequatenucleation layer atop the substrate surfaces. For example, the processgas may be flowed into the process chamber for a period of about 0.1seconds to about 90 seconds. In some time-domain ALD processes, thetungsten-containing gas is exposed the substrate surface for a time inthe range of about 0.1 sec to about 90 sec, or in the range of about 0.5sec to about 60 sec, or in the range of about 1 sec to about 30 sec, orin the range of about 2 sec to about 25 sec, or in the range of about 3sec to about 20 sec, or in the range of about 4 sec to about 15 sec, orin the range of about 5 sec to about 10 sec. The nucleation layer istypically deposited to a thickness in a range from about 10 Å to about200 Å and the bulk layer has a thickness in a range from about 100 Å toabout 10,000 Å, preferably in the range from about 1,000 Å to about5,000 Å. However, the thickness of these films can vary depending on thefeature sizes and aspect ratios of a given application.

In some embodiments, an inert gas may additionally be provided to theprocess chamber at the same time as the tungsten-containing gas. Theinert gas may be mixed with the tungsten-containing gas (e.g., as adiluent gas) or separately and can be pulsed or of a constant flow. Insome embodiments, the inert gas is flowed into the processing chamber ata constant flow in the range of about 1 to about 10000 sccm. The inertgas may be any inert gas, for example, such as argon, helium, neon,combinations thereof, or the like. In one or more embodiments, thetungsten-containing gas is mixed with argon prior to flowing into theprocess chamber.

The temperature of the substrate during deposition can be controlled,for example, by setting the temperature of the substrate support orsusceptor. In some embodiments the substrate is held at a temperature inthe range of about 300° C. to about 475° C., or in the range of about350° C. to about 450° C. In one or more embodiments, the substrate ismaintained at a temperature less than about 475° C., or less than about450° C., or less than about 425° C., or less than about 400° C., or lessthan about 375° C.

In addition to the foregoing, additional process parameters may beregulated while exposing the substrate to the tungsten-containingprocess gas. For example, in some embodiments, the process chamber maybe maintained at a pressure of about 0.3 to about 90 Torr.

In some embodiments, a low resistivity film (or a tunable grain sizefilm) is deposited using a combination of silane presoaking and ALD Wdeposition. For example, a substrate is soaked in substantially onlysilane before any ALD cycles (i.e., in step 603 of FIG. 6 ). Atungsten-containing precursor is co-flowed with a relatively low amountof hydrogen gas during the tungsten exposure step 606. The amount ofhydrogen co-flowed with the tungsten-containing precursor is low enoughso that there is substantially no CVD deposition. Relatively low flow ofhydrogen is relative to the amount of hydrogen needed for a reduction instep 610, not the amount of tungsten precursor being co-flowed. Forexample, hydrogen is co-flowed at about 5 sccm (where it is about 2000times greater for reductions). In some embodiments, the first reactivegas which contains the tungsten-containing compound and hydrogen hasmore hydrogen than tungsten on an atomic basis. In one or moreembodiments, the mixture of tungsten-containing precursor to hydrogen isin the range of about 1:2 to 1:20. The inventors have surprisingly foundthat a tungsten film deposited with processes using a silane soak andhydrogen co-flow has a higher grain size and a lower resistivity thanother processes. A 70 Å tungsten film deposited by a standard process(i.e., no silane presoak and/or no hydrogen co-flow) has a grain size of33 Å. The grain size for a 70 Å tungsten film using a silane soak andhydrogen co-flow is about 70 Å. In some embodiments, when the thicknessof the tungsten film is about 70 Å, the tungsten film has a grain sizegreater than or equal to about 60 Å or 65 Å. A 200 Å tungsten filmdeposited by a standard process has a resistivity of about 40 μΩ·cmwhile a film deposited by the silane soak and hydrogen co-flow processhas a resistivity of about 20 μΩ·cm. In some embodiments, when thetungsten film has a thickness of about 200 Å, the tungsten film has aresistivity less than or equal to about 20 μΩ·cm or 25 μΩ·cm.

Next, at step 608, the process chamber (especially in time-domain ALD)may be purged using an inert gas. (This may not be needed in spatial ALDprocesses as there is a gas curtain separating the reactive gases.) Theinert gas may be any inert gas, for example, such as argon, helium,neon, or the like. In some embodiments, the inert gas may be the same,or alternatively, may be different from the inert gas provided to theprocess chamber during the exposure of the substrate to the firstprocess gas at 606. In embodiments where the inert gas is the same, thepurge may be performed by diverting the first process gas from theprocess chamber, allowing the inert gas to flow through the processchamber, thereby purging the process chamber of any excess first processgas components or reaction byproducts. In some embodiments, the inertgas may be provided at the same flow rate used in conjunction with thefirst process gas, described above, or in some embodiments, the flowrate may be increased or decreased. For example, in some embodiments,the inert gas may be provided to the process chamber at a flow rate ofabout 0 to about 10000 sccm to purge the process chamber. In spatialALD, purge gas curtains are maintained between the flows of reactivegases and purging the process chamber may not be necessary. In someembodiment, however, the process chamber may be purged with an inertgas.

The flow of inert gas may facilitate removing any excess first processgas components and/or excess reaction byproducts from the processchamber to prevent unwanted gas phase reactions of the first and secondprocess gases. For example, the flow of inert gas may remove excesstungsten-containing gas from the process chamber, thereby preventing areaction between the tungsten precursor and a subsequent reactive gas.

Next, at step 610, the substrate is exposed to a second process gas fora second period of time. The second process gas reacts with thetungsten-containing compound on the substrate surface to create adeposited film. The second process gas can have an important impact onthe resulting tungsten film. For example, when the second process gas isH₂, a tungsten film is deposited, but when the second reactive gas issilane or disilane, a tungsten silicide film is deposited.

In some embodiments, the second reactive gas comprises hydrogen and theresulting film formed is a tungsten film. The hydrogen gas may besupplied to the substrate surface at a flow rate greater than thetungsten-containing gas concentration. In one or more embodiments, theflow rate of H₂ is greater than about 1 time that of thetungsten-containing gas, or about 100 times that of thetungsten-containing gas, or in the range of about 3000 to 5000 timesthat of the tungsten-containing gas. The hydrogen gas can be supplied,in time-domain ALD, for a time in the range of about 1 sec to about 30sec, or in the range of about 5 sec to about 20 sec, or in the range ofabout 10 sec to about 15 sec. The hydrogen gas can be supplied at apressure in the range of about 1 Torr to about 30 Torr, or in the rangeof about 5 Torr to about 25 Torr, or in the range of about 10 Torr toabout 20 Torr, or up to about 50 Torr. The substrate temperature can bemaintained at any suitable temperature. In one or more embodiments, thesubstrate is maintained at a temperature less than about 475° C., or ata temperature about the same as that of the substrate during thetungsten-containing film deposition.

In some embodiments, conformal coverage of a feature is performed usingshort step times in both the pulse and purge steps, typically about 1-2seconds. This time is sufficient for a reasonable adsorption of theprecursor onto the substrate surface in the pulse step and for purgingaway the excess precursors or reduction gases from the gas delivery pathas well as chamber cavity in the purge step. As used in thisspecification and the appended claims, the term “reasonable adsorption”is enough adsorption for a film to grow. In some embodiments, a tungstenfilm is grown at a rate less than or equal to about 0.9 Å/cycle, 0.8Å/cycle. 0.7 Å/cycle, or 0.6 Å/cycle. Lower growth rates are good forconformal growth whereas higher growth rates (e.g., above about 1Å/cycle) tend to grow non-conformal films. One or more embodiments, ofthe invention are directed to conformal tungsten films.

In some embodiments, the second reactive gas comprises hydrogenradicals. The hydrogen radicals can be generated by any suitable meansincluding exposure of hydrogen gas to a “hot-wire”. As used in thisspecification and the appended claims, the term “hot-wire” means anyelement that can be heated to a temperature sufficient to generateradicals in a gas flowing about the element. This is also referred to asa heating element.

Accordingly, one or more embodiments of the invention are directed tomethods of processing a substrate or depositing a film. At least aportion of the substrate is sequentially exposed to a first reactive gascomprising a metal complex and a second reactive gas. The metal complexcan be any suitable metal complex for ALD processing including, but notlimited to, organometallic complexes. In some embodiments, theorganometallic complex comprises a tungsten-containing compound. Thetungsten-containing compound of some embodiments has the empiricalformula WCl₅ (e.g., WCl₅, W₂Cl₁₀). In one or more embodiments, thetungsten-containing compound has the empirical formula WCl₆ (e.g., WCl₆,W₂Cl₁₂). The second reactive gas may comprise hydrogen radicals. Themethod of some embodiments is practices in a spatial atomic layerdeposition chamber or by a spatial atomic layer deposition process.Spatial ALD may be particularly effective in the deposition of atungsten film with hydrogen radicals because the device used to generateradicals (e.g., a hot wire) can be isolated from the metal organicprecursors which are often incompatible with the hot wire material.

The second reactive gas (e.g., hydrogen), while passing the hot wire, orheating element, becomes radicalized. For example, H₂ passing a hottungsten wire can result in the generation of H*. These hydrogenradicals are more reactive than ground state hydrogen atoms.

To be effective, the heating element must be heated to a temperaturesufficient to create radicals. Heating can occur by, for example,passing sufficient electrical current through the heating element toelevate the temperature of the heating element.

Next, at 612, process chamber may be purged using an inert gas. Theinert gas may be any inert gas, for example, such as argon, helium,neon, or the like. In some embodiments, the inert gas may be the same,or alternatively, may be different from the inert gas provided to theprocess chamber during previous process steps. In embodiments where theinert gas is the same, the purge may be performed by diverting thesecond process gas from the process chamber, allowing the inert gas toflow through the process chamber, thereby purging the process chamber ofany excess second process gas components or reaction byproducts. In someembodiments, the inert gas may be provided at the same flow rate used inconjunction with the second process gas, described above, or in someembodiments, the flow rate may be increased or decreased. For example,in some embodiments, the inert gas may be provided to the processchamber at a flow rate of about 0 to about 10,000 sccm to purge theprocess chamber.

While the generic embodiment of the processing method shown in FIG. 1includes only two pulses of reactive gases, it will be understood thatthis is merely exemplary and that additional pulses of reactive gasesmay be required. For example, a nitride film of some embodiments can begrown by a first pulse containing a precursor gas like tungstenpentachloride, a second pulse with a reducing agent followed by purgingand a third pulse for nitridation. The pulses can be repeated in theirentirety or in part. For example all three pulses could be repeated oronly two can be repeated. This can be varied for each cycle as desired.

Next, at 614, it is determined whether the tungsten-containing layer hasachieved a predetermined thickness. If the predetermined thickness hasnot been achieved, the method 600 returns to 604 to continue forming thetungsten-containing layer until the predetermined, or desired, thicknessis reached. Once the predetermined thickness has been reached, themethod 600 can either end or proceed to 116 where a bulk depositionprocess may be performed to deposit the remaining thickness of thetungsten-containing layer. In some embodiments, the bulk depositionprocess may be a CVD process. Upon completion of deposition of thetungsten-containing layer to a desired thickness, the method 600generally ends and the substrate can proceed for any further processing.For example, in some embodiments, a CVD process may be performed to bulkdeposit the tungsten-containing layer to a target thickness. For examplein some embodiments, the tungsten-containing layer may be deposited viaALD or CVD reaction of the tungsten precursor and hydrogen radicals toform a total layer thickness of about 10 to about 10,000 Å, or in someembodiments, about 10 to about 1000 Å, or in some embodiments, about 500to about 5,000 Å.

While the descriptions have generally referred to thetungsten-containing gas as the first gas, it will be understood by thoseskilled in the art that this is merely illustrative. In someembodiments, the substrate is first exposed to the second reactive gasfollowed by the tungsten-containing gas.

In any of the above embodiments, each cycle consisting of exposing thesubstrate to a first process gas, purging with an inert gas, exposingthe substrate to a second process gas, and purging with an inert gas mayform a tungsten-containing layer having a thickness of about 0.1 toabout 1.5 Å on the substrate. In some embodiments, the thickness growsat a rate in the range of about 0.1 Å/cycle to about 5 Å/cycle, or inthe range of about 0.2 Å/cycle to about 3 Å/cycle, or in the range ofabout 0.3 Å/cycle to about 2 Å/cycle. The sequence may be repeated untila desired total thickness of the tungsten-containing layer is achieved.For example, in some embodiments, the tungsten-containing layer maycomprise a total thickness of about 2 Å to about 200 Å, or in someembodiments, about 50 Å. Accordingly, the deposition process may requireup to about 2000 cycles to reach the desired thickness.

In any of the above embodiments, the flow rates and/or durations of eachpulse may be the same or may vary over the course of the total cyclesrequired to form a particular tungsten-containing layer, therebyfacilitating layers having either uniform or graded compositions.

In some embodiments, the substrate surface is preconditioned. Forexample, if the surface of the substrate is an oxide, it may bedesirable to perform a pre-soak using a hydride or hydride/hydrogenmixture. The hydride adsorbs and/or reacts with the substrate surface toform a conditioned surface, allowing for a uniform tungsten-containinglayer to be formed. In some embodiments, the hydride may comprise silane(Si_(x)H_(y)) compounds (e.g., silane (SiH₄), disilane (Si₂H₆),trisilane (Si₃H₈), chlorosilane, dichlorosilane (H₂SiCl₂), or the like),borane (B_(x)H_(y)) compounds (e.g., diborane (B₂H₆), triborane (B₃H₈),pentaborane (B₅H₉), or the like), phosphine (PH₃), derivatives thereof,combinations thereof, or the like. In addition, in some embodiments, thehydride may be diluted in a dilutant gas, for example an inert gas, suchas argon (Ar), helium (He), nitrogen (N₂), hydrogen (H₂), or the like.For example, in such embodiments, the hydride may be provided in amixture of about 5% hydride to about 95% diluent gas by volume. In someembodiments, for example where the hydride comprises diborane, the flowrate of the hydride may be about 1 to about 75 sccm.

In an embodiment, a tungsten film may be formed by placing a substratewith 10 Å or more of a metallic layer, such as ALD TiN, TiSiN, TiAl, PVDTi, TiN, or, if an oxide, soak with either disilane or a mixture ofhydrogen and silane at 5 to 20 Torr partial pressure on a pedestal heldat a temperature in the range of about 400 to about 475° C. Atungsten-containing compound (e.g., WCl₅ or WCl₆) can be pulsed with amixture of argon to the wafer surface at 5 to 20 Torr followed bypurging with argon (or another inert gas). Argon pressure is increasedto about 20 Torr and then hydrogen pulsing is started. The hydrogenradical pulsing may be done at high flow so that the ratio of hydrogento tungsten-containing compound is in the range of about 3000 to 5000,for about 10 to 15 seconds. The chamber is purged with argon (or anotherinert gas) for 5 to 10 seconds. The cycle is repeated until the growthof the tungsten film reaches a designated thickness.

Some embodiments of the invention are directed to tungsten containingfilms. These film include, tungsten metal films, tungsten nitrides,silicide and tungsten silicon nitride. The tungsten containing films canbe used for any number of suitable purposes including, but not limitedto, p-metal work function layers and fill materials.

Accordingly, some embodiments of the invention are directed tofluorine-free tungsten films used as the p-metal work function layer tomanufacture metal gates in field effect transistor (FET) devices, inboth logic and memory applications. The film grown by the describedprocesses has significant benefits including a significantly lowerresistivity and higher thermal stability (can be annealed up to 1000°C.) than other films currently used as a gate metal. The thermalstability is especially important for VNAND and BWL in memoryapplications. One or more embodiments of the invention are directed totungsten films having a work function greater than about 4.6 eV or about4.7 eV, or about 4.8 eV. The work function metal can be deposited on agate oxide of the FET. The work function metal controls the thresholdvalue for current flow. A low threshold value requires less energy usageso a more conductive metal is better. Tungsten films deposited by knownprocesses results in a film typically with a work function of about 4.45eV.

Some embodiments of the invention are directed to integrated circuittransistor devices comprising a dielectric layer disposed over achannel. A work function metal is disposed over the dielectric layer anda fill layer consisting essentially of tungsten is deposited over thework function layer. As used in this specification and the appendedclaims, the term “consisting essentially of tungsten” used in thisregard means that the fill layer is greater than about 95%, 98% or 99%tungsten. The work function layer of some embodiments comprises one ormore of Ti and TiAl. In one or more embodiments, the work function metalcontains substantially no fluorine. In some embodiments, the fill layercontains substantially no fluorine. As used in this specification andthe appended claims, the term “substantially no fluorine” means thatthere is less than about 5%, 4%, 3%, 2%, 1%, 0.5% or 0.1% fluorine inthe film on an atomic basis. In some embodiments, there is nointervening layer between the work function metal and the filmconsisting essentially of tungsten.

In one or more embodiments, there is an intervening layer between thework function metal and the film consisting essentially of tungsten. Theintervening layer can have any suitable thickness depending on theintended use of the integrated circuit transistor. In some embodiments,the intervening layer has a thickness less than about 7 Å, 6 Å, 5 Å, 4 Åor 3 Å.

In some embodiments, the tungsten containing film is used as a lowresistivity fill material. To achieve a complete seamless fill, aperiodic treatment (e.g., after every 10 to 30 Å film) is applied. Themethod of the treatment includes (a) alternating exposure to TiCl₄ andammonia; (b) performing a TiCl₄ soak or (c) hydrogen direct or remoteplasma exposure for 10 to 30 seconds. The treatment can be performed atthe same temperature as the deposition process. The processes describedwill deposit about 0.7 Å TiN (less than 1 Å TiN) to refresh the surfaceand remove extra chloride during deposition. The amount of TiN depositedin these embodiments is less than about ½ a monolayer or in the range ofabout ⅓ to about ⅕ of a monolayer of TiN.

It has been found that the various tungsten films described can beuseful for, for example, (1) nucleation and film growth repeatabilityusing a silane soak; (2) adhesions on oxides by growing an initial oneor two layers of tungsten silicide; (3) reducing roughness by soaking inammonia, followed by soaking in silane (to increase nucleation density)(4) by TiCl₄/NH₃ cycles (on oxide or oxidized surface) to deposit lessthan about 1 Å TiN at the interface; and (5) integration of thin TiN, toprovide good nucleation, adhesion and conformality (deposited by anysuitable method and reagents).

According to one or more embodiments, the substrate is subjected toprocessing prior to and/or after forming the layer. This processing canbe performed in the same chamber or in one or more separate processingchambers. In some embodiments, the substrate is moved from the firstchamber to a separate, second chamber for further processing. Thesubstrate can be moved directly from the first chamber to the separateprocessing chamber, or it can be moved from the first chamber to one ormore transfer chambers, and then moved to the separate processingchamber. Accordingly, the processing apparatus may comprise multiplechambers in communication with a transfer station. An apparatus of thissort may be referred to as a “cluster tool” or “clustered system,” andthe like.

Generally, a cluster tool is a modular system comprising multiplechambers which perform various functions including substratecenter-finding and orientation, annealing, annealing, deposition and/oretching. According to one or more embodiments, a cluster tool includesat least a first chamber and a central transfer chamber. The centraltransfer chamber may house a robot that can shuttle substrates betweenand among processing chambers and load lock chambers. The transferchamber is typically maintained at a vacuum condition and provides anintermediate stage for shuttling substrates from one chamber to anotherand/or to a load lock chamber positioned at a front end of the clustertool. Two well-known cluster tools which may be adapted for the presentdisclosure are the Centura® and the Endura®, both available from AppliedMaterials, Inc., of Santa Clara, Calif. However, the exact arrangementand combination of chambers may be altered for purposes of performingspecific steps of a process as described herein. Other processingchambers which may be used include, but are not limited to, cyclicallayer deposition (CLD), atomic layer deposition (ALD), chemical vapordeposition (CVD), physical vapor deposition (PVD), etch, pre-clean,chemical clean, thermal treatment such as RTP, plasma nitridation,anneal, orientation, hydroxylation and other substrate processes. Bycarrying out processes in a chamber on a cluster tool, surfacecontamination of the substrate with atmospheric impurities can beavoided without oxidation prior to depositing a subsequent film.

According to one or more embodiments, the substrate is continuouslyunder vacuum or “load lock” conditions, and is not exposed to ambientair when being moved from one chamber to the next. The transfer chambersare thus under vacuum and are “pumped down” under vacuum pressure. Inertgases may be present in the processing chambers or the transferchambers. In some embodiments, an inert gas is used as a purge gas toremove some or all of the reactants. According to one or moreembodiments, a purge gas is injected at the exit of the depositionchamber to prevent reactants from moving from the deposition chamber tothe transfer chamber and/or additional processing chamber. Thus, theflow of inert gas forms a curtain at the exit of the chamber.

The substrate can be processed in single substrate deposition chambers,where a single substrate is loaded, processed and unloaded beforeanother substrate is processed. The substrate can also be processed in acontinuous manner, similar to a conveyer system, in which multiplesubstrate are individually loaded into a first part of the chamber, movethrough the chamber and are unloaded from a second part of the chamber.The shape of the chamber and associated conveyer system can form astraight path or curved path. Additionally, the processing chamber maybe a carousel in which multiple substrates are moved about a centralaxis and are exposed to deposition, etch, annealing, cleaning, etc.processes throughout the carousel path.

During processing, the substrate can be heated or cooled. Such heatingor cooling can be accomplished by any suitable means including, but notlimited to, changing the temperature of the substrate support andflowing heated or cooled gases to the substrate surface. In someembodiments, the substrate support includes a heater/cooler which can becontrolled to change the substrate temperature conductively. In one ormore embodiments, the gases (either reactive gases or inert gases) beingemployed are heated or cooled to locally change the substratetemperature. In some embodiments, a heater/cooler is positioned withinthe chamber adjacent the substrate surface to convectively change thesubstrate temperature.

The substrate can also be stationary or rotated during processing. Arotating substrate can be rotated continuously or in discreet steps. Forexample, a substrate may be rotated throughout the entire process, orthe substrate can be rotated by a small amount between exposures todifferent reactive or purge gases. Rotating the substrate duringprocessing (either continuously or in steps) may help produce a moreuniform deposition or etch by minimizing the effect of, for example,local variability in gas flow geometries.

In atomic layer deposition type chambers, the substrate can be exposedto the first and second precursors either spatially or temporallyseparated processes. Temporal ALD is a traditional process in which thefirst precursor flows into the chamber to react with the surface. Thefirst precursor is purged from the chamber before flowing the secondprecursor. In spatial ALD, both the first and second precursors aresimultaneously flowed to the chamber but are separated spatially so thatthere is a region between the flows that prevents mixing of theprecursors. In spatial ALD, the substrate is moved relative to the gasdistribution plate, or vice-versa.

In embodiments, where one or more of the parts of the methods takesplace in one chamber, the process may be a spatial ALD process. Althoughone or more of the chemistries described above may not be compatible(i.e., result in reaction other than on the substrate surface and/ordeposit on the chamber), spatial separation ensures that the reagentsare not exposed to each in the gas phase. For example, temporal ALDinvolves the purging the deposition chamber. However, in practice it issometimes not possible to purge the excess reagent out of the chamberbefore flowing in additional regent. Therefore, any leftover reagent inthe chamber may react. With spatial separation, excess reagent does notneed to be purged, and cross-contamination is limited. Furthermore, alot of time can be used to purge a chamber, and therefore throughput canbe increased by eliminating the purge step.

Reference throughout this specification to “one embodiment,” “certainembodiments,” “one or more embodiments” or “an embodiment” means that aparticular feature, structure, material, or characteristic described inconnection with the embodiment is included in at least one embodiment ofthe disclosure. Thus, the appearances of the phrases such as “in one ormore embodiments,” “in certain embodiments,” “in one embodiment” or “inan embodiment” in various places throughout this specification are notnecessarily referring to the same embodiment of the disclosure.Furthermore, the particular features, structures, materials, orcharacteristics may be combined in any suitable manner in one or moreembodiments.

Although the disclosure herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent disclosure. It will be apparent to those skilled in the art thatvarious modifications and variations can be made to the method andapparatus of the present disclosure without departing from the spiritand scope of the disclosure. Thus, it is intended that the presentdisclosure include modifications and variations that are within thescope of the appended claims and their equivalents.

What is claimed is:
 1. A method comprising: exposing a substrate surfaceto a first process condition, the first process condition comprising aconstant flow of a first reactive gas and a pulsed flow of a secondreactive gas, the second reactive gas pulsed so that there is less thana full amount of the second reactive gas for CVD; purging the substratesurface of the first process condition to remove the first reactive gasand the second reactive gas; and exposing the substrate surface to asecond process condition comprising the second reactive gas.
 2. Themethod of claim 1, wherein the first reactive gas comprises WF₆.
 3. Themethod of claim 2, wherein the second reactive gas comprises H₂.
 4. Themethod of claim 1, wherein the second reactive gas comprises in therange of about 1 to about 10% of the first reactive gas in the firstprocess condition.
 5. The method of claim 1, wherein a film is depositedwith a deposition rate in the range of about 0.2 to about 1 Å/cycle. 6.The method of claim 1, further comprising purging the substrate surfaceof the second process condition and repeating exposure to the firstprocess condition, purging of the substrate surface and exposure to thesecond process condition.
 7. The method of claim 1, wherein thesubstrate surface is positioned within a processing chamber and purgingthe substrate surface comprises purging the processing chamber.
 8. Amethod comprising: exposing a substrate surface to a first processcondition comprising a constant flow of a first reactive gas and asecond reactive gas, the first reactive gas and the second reactive gasare spontaneously reactive; purging the substrate surface of the firstprocessing condition to remove the first reactive gas and the secondreactive gas; and exposing the substrate surface to a second processcondition consisting essentially of the second reactive gas, wherein thefirst process condition comprises less than a full amount of the secondreactive gas for CVD.
 9. The method of claim 8, wherein the firstreactive gas comprises WF₆.
 10. The method of claim 9, wherein thesecond reactive gas consists essentially of H₂.
 11. The method of claim8, wherein the second reactive gas is pulsed into the first reactive gasin the first process condition.
 12. The method of claim 8, wherein thesecond reactive gas is continuously flowed into the first reactive gasin the first process condition.
 13. The method of claim 8, wherein thesecond reactive gas comprises in the range of about 1 to about 10% ofthe first reactive gas in the first process condition.
 14. The method ofclaim 8, wherein a film is deposited with a deposition rate in the rangeof about 0.2 to about 1 Å/cycle.
 15. The method of claim 8, wherein thesubstrate surface is positioned within a processing chamber and purgingthe substrate surface comprises purging the processing chamber.
 16. Themethod of claim 8, wherein the substrate surface is positioned within aprocessing chamber and purging the substrate surface comprises purgingthe processing chamber.
 17. A method comprising: exposing a substratesurface to a first process condition in a first process region of aprocessing chamber, the first process condition comprising a constantflow of a first reactive gas comprising WF₆ and a pulsed flow of asecond reactive gas consisting essentially of H₂, the second reactivegas pulsed so that there is less than a full amount of the secondreactive gas for CVD; purging the substrate surface of the firstprocessing condition to remove the WF₆ and the H₂; exposing thesubstrate surface to a second process condition in the second processregion, the second process condition consisting essentially of the H₂;purging the substrate surface of the second processing condition; andrepeating exposure to the first process condition, purge of thesubstrate surface, and exposure to the second process condition todeposit a film of a predetermined thickness.